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William
2010-Feb-20, 04:39 PM
In the last decade it has been found the geomagnetic field abruptly changes in inclination roughly every 500 years. (archeomagnetic jerks.)

In addition it was been found the geomagnetic field also abruptly drops in magnitude every 30 kyr.

This paper by Ryskin hypothesizes that the modulation of the geomagnetic field could be due to changes in ocean currents.

One problem with Ryskin's hypothesize is there is no mechanism to cyclically abruptly change ocean currents.

Ryskin needs to correlate past massive ocean current changes to past massive geomagnetic changes.

As others have shown there is correlation to paleoclimatic abrupt climate change and geomagnetic field changes. The archeomagnetic jerk field changes can be limited to a hemisphere and to one part of a hemisphere. (Think of the current South Atlantic geomagnetic anomaly which is localized in the vicinity of South America.)

As noted in the forum there is evidence of burn marks on the surface of the earth that coincides with the Younger Dryas abrupt cooling event (11,800 years ago. Younger Dryas cooling event is the largest climate change in the last 12,000 years. The Younger Dryas abrupt climate change event occurred in less than the decade. The Younger Dryas cooling lasted for around a 1000 years. The planet changed from interglacial warm back to glacial cold at a time when insolation at 65N was maximum.) There is a geomagnetic excursion that coincides with the timing of the Younger Dryas cooling event.

The Younger Dryas abrupt climate change event is only one of series of abrupt climate change events.

If a cyclic abrupt change in the geomagnetic field is the cause of the cyclic abrupt climate change events, then there is a cyclic mechanism that modulates the geomagnetic field.

If whatever caused the Younger Dryas burn marks in multiple location in the Northern Hemisphere is what is causing the cyclic geomagnetic field changes, that specific event that caused the burn marks is also cyclic. If that statement is correct, there will in future be more burn marks created on the surface of the planet which will again change the geomagnetic field.

Now if the Younger Dryas burn marks were created by a cyclic solar event it would seem the same solar event should affect the planetary magnetic field of the other planets in the solar system. Is there any evidence of that occurring? Yes. See next comment.

http://www.iop.org/EJ/abstract/1367-2630/11/6/063015/

http://www.sciencedaily.com/releases/2009/06/090615094038.htm


Secular variation of the Earth's magnetic field: induced by the ocean flow?

Secular variation of the Earth's main magnetic field is believed to originate in the Earth's core. (The main field is operationally defined as comprising spherical harmonics of degree l≤10.) I propose a different mechanism of secular variation: ocean water being a conductor of electricity, the magnetic field induced by the ocean as it flows through the Earth's main field may depend on time and manifest itself globally as secular variation. This proposal is supported by calculation of secular variation using the induction equation of magnetohydrodynamics, the observed main field and the ocean flow field. The predicted secular variation is in rough agreement with that observed. Additional support is provided by the striking temporal correlation (hitherto unsuspected) between the intensity of the North Atlantic oceanic circulation and the rate of secular variation in Western Europe; this explains, in particular, the geomagnetic jerks, and the recently discovered correlation between secular variation and climate. Spatial correlation between ocean currents and secular variation is also strong.


http://geosci.uchicago.edu/~rtp1/BardPapers/responseCourtillotEPSL07.pdf



Also, we wish to recall that evidence of a correlation between archeomagnetic jerks and cooling events (in a region extending from the eastern North Atlantic to the Middle East) now covers a period of 5 millenia and involves 10 events (see f.i. Figure 1 of Gallet and Genevey, 2007). The climatic record uses a combination of results from Bond et al (2001), history of Swiss glaciers (Holzhauser et al, 2005) and historical accounts reviewed by Le Roy Ladurie (2004). Recent high-resolution paleomagnetic records (e.g. Snowball and Sandgren, 2004; St-Onge et al., 2003) and global geomagnetic field modeling (Korte and Constable, 2006) support the idea that part of the centennial-scale fluctuations in 14C production may have been influenced by previously unmodeled rapid dipole field variations. In any case, the relationship between climate, the Sun and the geomagnetic field could be more complex than previously imagined. And the previous points allow the possibility for some connection between the geomagnetic field and climate over these time scales.



http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf



If solar activity is correlated to climate over much of historical times, it might be expected that the “overall magnetic trend” would correlate with the recent evolution of global temperature, and this is indeed the case up to the mid-1980s, but not since then (Fig. 3). Of course, the relation is this case does not imply a causal link from Earth's magnetism towards climate, but from the Sun to both climate and magnetic changes. Clearly, 100 yr is not enough to ascertain that such a correlation is robust, but it is as impressive as many of the correlations of time series proposed over this time range.

Archeomagnetic jerks are found around 1400, 800, 200AD and 800 BC. Subsequent work [61] has added an event around 1600, with other less robust possibilities at 1800, 600 AD and 350 BC. This implies 4 rather clear events in the past two millennia (i.e. a “repeat time” on the order of 500 yr, a time-constant characteristic of secular variation of the equatorial dipole field — e.g. [57]) if only the more robust events are included. The number goes to 7 if all suggested events are included, implying a time constant of 200–300 yr, not very different from the duration of the events themselves and more characteristic of non-dipole secular variation (though see [53]). In this paper, we restrict ourselves to the better-identified events, which remain short and rather rare on the time scales considered.

There is a good correspondence between jerk times (particularly their rising period) and advances in glaciers. The correlation between cold events and archeomagnetic jerks is significant at 1600, ~1350, ~800 AD and ~800 BC. Very recently, Gallet et al. [64] have extended the database to 3000 BC in the Middle East, and found older jerk events at ~1600, ~2100 and ~2700 BC (Fig. 5; see also [59]). They found that these geomagnetic variations coincide in time with cooling periods detected in the North Atlantic from ice-rafted debris [65].

William
2010-Feb-20, 05:05 PM
The expectation is that the planetary magnetic fields should be aligned with the planet's axis of rotation.

That is true for the Earth, Jupiter, and Saturn. It is not true for Uranus and Neptune. Uranus and Neptune's magnetic field is aligned with the planet's orbit around the sun rather than with planet's rotational axis. In addition the Uranus and Neptune's magnetic field's axis is off set from the Uranus and Neptune's planetary axis of rotation.

The finding that earth's magnetic field is cyclic and abruptly changing inclination is interesting.

If the planetary field was only due to movement of a conductive liquid which creates the planet's magnetic field, then Uranus and Neptune would need to have a conductive liquid that is off set from the planet's axis of rotation and would need to have specific movements of conductive liquid that would need to produce a magnetic field is 60 degrees inclined from the planet's axis of rotation.

The appeal to a conductive liquid that is off set from the planet's axis of rotation does not seem physically reasonable, as gravity, density, difference, and time should have resulted in a stratified mantel in Uranus and Neptune. I do not see any means to create motion in the conductive liquid that is off set from the axis of rotation to create a planetary magnetic field that is aligned with the planet orbital rotation about the sun.

The finding of an observation that cannot be explained by a mechanism is a paradox.



The New Solar System, 4th Edition by J. Beatth, C. Peterson, A Chaikin

As Voyager approached Uranus in January 1986, we wondered if our experiences with symmetric magnetic environments of Earth, Jupiter, and Saturn would true for a planet that is quite literally spinning on its side. (My comment in relationship to Uranus’ orbit about the sun.)

An empirical relationship that relates angular momentum and magnetic moments, the “Bode’s law” of planetary magnetism, suggested that the magnetic moment of Uranus would be about one-tenth of Saturn.

We knew that the rotational axis of Uranus would lie, in early 1986, within 8 degrees of the planet-Sun line. If Uranus’s magnetic and rotational axis were nearly parallel, as is the case for other magnetized planets, (my comment in planets in the solar system), one pole would be pointed almost directly at the Sun and the a very unusual magnetospheric shape would be expected.

The planet’s magnetic moment is nearly the same strength as that predicted, but orientation is very different from our expectations. Uranus’ magnetic axis is tilted at huge 59 degrees from Uranus’s rotational axis and offset from the planet’s center.

Figure 18
The magnetic fields of Uranus and Neptune are remarkably – and unexpectedly – alike. The large offset from centre means that the field strength … It also means that the fields source cannot lie in the cores but rather must in a turbulent liquid mantle where dynamo driving convection can be substained.

G O R T
2010-Feb-21, 10:21 AM
The idea here seems to be that ocean currents are the major (if not the only) influence on the Earths magnetic field, and by proxy the climate.

Please explain the relationship of ocean currents to this Global Magnetic Anomaly Map (http://projects.gtk.fi/export/sites/projects/WDMAM/project/perugia/WDMAM_1.02_2007_Edition_low_resolution_reduced1.pd f).

If geomagnetic changes affect climate, why is this not evident when comparing geomagnetic reversals to known climate changes?

Why do you refer to formations like the Carolina bays as burn marks?

Since the formation of individual Carolina bays have been dated anywhere from 100kya to 12kya, why do you refer to only the Younger Dryas?

Where does this expectation that a planetary magnetic field should be aligned with the planet's axis of rotation come from? What makes you think that a snapshot of conditions at the present time constitutes a permanent condition, or even the norm?

hhEb09'1
2010-Feb-21, 12:01 PM
Why do you refer to formations like the Carolina bays as burn marks? That isn't in this thread, is it?

I did a search for William's past posts and found his thread 500,000 Elliptical Burn Marks. Cause? (http://www.bautforum.com/against-mainstream/80421-500-000-elliptical-burn-marks-cause.html) which had been moved into ATM. Is this thread more of the same?

William
2010-Feb-21, 06:54 PM
That isn't in this thread, is it?

I did a search for William's past posts and found his thread 500,000 Elliptical Burn Marks. Cause? (http://www.bautforum.com/against-mainstream/80421-500-000-elliptical-burn-marks-cause.html) which had been moved into ATM. Is this thread more of the same?

No hhEb09,

This thread is about the new observations which are unexplained.

We now have discovered archeomagnetic jerks where the geomagnetic field abruptly changes inclination. Ten such jerks have been found in the last 5000 years. Abrupt climate changes coincide with the archeomagnetic jerks.

We have now discovered that was a geomagnetic field excursion that coincides with the 12,900 year ago Younger Dryas abrupt cooling event.

We are now aware that the Younger Dryas event is one a cycle of such abrupt cooling events.

And lastly there is this paper that shows the burn marks that occur all over the Northern Hemisphere which coincide with Younger Dryas event were not caused by extraterrestrial objects that burns the earth but does not create impact craters.

http://www.pnas.org/content/106/43/18155


An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis

Based on elevated concentrations of a set of “impact markers” at the onset of the Younger Dryas stadial from sedimentary contexts across North America, Firestone, Kennett, West, and others have argued that 12.9 ka the Earth experienced an impact by an extraterrestrial body, an event that had devastating ecological consequences for humans, plants, and animals in the New World [Firestone RB, et al. (2007) Proc. Natl. Acad. Sci. USA 104:16016–16021]. Herein, we report the results of an independent analysis of magnetic minerals and microspherules from seven sites of similar age, including two examined by Firestone et al. We were unable to reproduce any results of the Firestone et al. study and find no support for Younger Dryas extraterrestrial impact.

William
2010-Feb-21, 07:32 PM
The idea here seems to be that ocean currents are the major (if not the only) influence on the Earths magnetic field, and by proxy the climate.

Please explain the relationship of ocean currents to this Global Magnetic Anomaly Map (http://projects.gtk.fi/export/sites/projects/WDMAM/project/perugia/WDMAM_1.02_2007_Edition_low_resolution_reduced1.pd f).

If geomagnetic changes affect climate, why is this not evident when comparing geomagnetic reversals to known climate changes?

Why do you refer to formations like the Carolina bays as burn marks?

Since the formation of individual Carolina bays have been dated anywhere from 100kya to 12kya, why do you refer to only the Younger Dryas?

Where does this expectation that a planetary magnetic field should be aligned with the planet's axis of rotation come from? What makes you think that a snapshot of conditions at the present time constitutes a permanent condition, or even the norm?

GORT,

Ryskin's ocean current modulation of the geomagnetic field hyothesis is not correct. The geomagnetic field abruptly changed inclination 10 times in the last 5000 years. There is no mechanism that can abruptly change the ocean current 10 times in the last 5000 years.

Now as to the affect of a geomagnetic field excursion on the planet's climate. The planet is very cold when the geomagnetic field excursion occurs. The GCR affect saturates. Additional GCR has less and less effect. More GCR does not create additional clouds. The change in the geomagnetic field inclination changes where the clouds are formed. That explains why there is unexplained warming and cooling when the inclination occurs. Further complicating the paleo analysis is the geomagnetic intensity can when it equalizes increase or decrease intensity depending on the hemisphere where the strike occurred.

What has sufficient power to abruptly change the inclination of the geomagnetic field 10 times in the last 5000 years?

This is not a theoretical thread. There is a massive cycle event that is occurring that will have a significant affect on the biosphere. There is observational evidence of burn marks at multiple locations in the Northern Hemisphere that all coincide in time with the Younger Dryas abrupt cooling event. There is observational evidence of a massive ribbon of gas at the far edge of the solar system that is aligned at 90 degrees to the planet's orbits. There is the curious offset Uranus and Neptune planetary magnetic fields.

It seems logical that a cyclic abrupt change to the geomagnetic field would have a cyclic forcing function. As we have never seen an event that leaves massive burn marks on the surface of the planet, it likely seems unimaginable. The basic implication is that the sun from time to time becomes unstable. The solar instability it appears comes in a small, medium, large, and super large.

Read through this paper which is the author's response to comments.


“Are there connections between Earth’s magnetic field and climate?, Earth Planet. Sci. Lett., 253, 328–339, 2007” by Bard, E., and Delaygue, M., Earth Planet. Sci. Lett., in press, 2007

http://geosci.uchicago.edu/~rtp1/BardPapers/responseCourtillotEPSL07.pdf

Also, we wish to recall that evidence of a correlation between archeomagnetic jerks and cooling events (in a region extending from the eastern North Atlantic to the Middle East) now covers a period of 5 millenia and involves 10 events (see f.i. Figure 1 of Gallet and Genevey, 2007). The climatic record uses a combination of results from Bond et al (2001), history of Swiss glaciers (Holzhauser et al, 2005) and historical accounts reviewed by Le Roy Ladurie (2004). Recent high-resolution paleomagnetic records (e.g. Snowball and Sandgren, 2004; St-Onge et al., 2003) and global geomagnetic field modeling (Korte and Constable, 2006) support the idea that part of the centennial-scale fluctuations in 14C production may have been influenced by previously unmodeled rapid dipole field variations. In any case, the relationship between climate, the Sun and the geomagnetic field could be more complex than previously imagined. And the previous points allow the possibility for some connection between the geomagnetic field and climate over these time scales.

We first reiterate the fact that the “claims” made in our paper regarding correlations between cooling periods and archeomagnetic jerks were actually put forward by
Gallet et al (2005, 2006). We do note that the causal relationship between cosmic ray flux and cloud cover suggested by Marsh and Svensmark (2000) would result in a correlation opposite to the one we find if the field geometry were axial and dipolar and this is precisely why we propose a mechanism of dipole tilt or non dipole geometry to interpret our observations. Gallet et al (2005) write: “ Another hypothesis is to assume that the incoming charged particles are deflected towards the poles, where the overall low humidity level due to cold temperatures limits cloud formation. If archeomagnetic jerks indeed correspond to periods of strongly inclined dipole, then the charged particles would interact with more humid air from lower latitude environments, leading to significantly larger cloud production and cooling.” And if this happens, there is no need to “overcome the more direct effect", as (mis)understood by BD07 (who seem to understand that a growing axial dipole is superimposed on a tilted dipole, which is not the case).

Ara Pacis
2010-Feb-22, 12:23 AM
I'm not qualified to examine the claims but I have what may be some useful observations.

Glaciation locks up freshwater on the continents. This causes:
Changes in ocean salinity
Alterations to the Earth's rotation via mass distribution and tides
Isostatic changes to the Earth's mantle due to mass distribution
changes in lubrication of tectonic faults

If I recall correctly, some theories posit warped slabs of cooler crust material have descended down subduction zones and pile up at the interface of the lower mantle and the outer core.

I do not know if any of these possible phenomena can have a significant enough effect on the Earth's magnetic field via electromagnetic or mechanical means.

William
2010-Feb-22, 01:54 AM
If geomagnetic changes affect climate, why is this not evident when comparing geomagnetic reversals to known climate changes?



Hi GORT,

The paper I linked to above shows there are climate change events that coincide with the 10 geomagnetic jerk events that have occurred in the last 5000 years. The geomagnetic jerks are abrupt changes in the geomagnetic field inclination. As noted in my above comment if the excursion occurs in the middle of a very cold glacial period the weaker geomagnetic field does not result in more planetary cloud, as the planet is so cold there is very little water vapor to form clouds.

As the authors of the paper linked to below note, the end of the past interglacials has coincided with a geomagnetic excursions which results in a low in geomagnetic field strength. The interglacial periods correlate with a high geomagnetic field strength. The very large climate changes (end of interglacial and start of interglacial) correlate inversely with a sudden drop in magnetic field strength and with an increase in magnetic field strength.)

To understand the mechanisms it is necessary to apply Svensmark's mechanism to the earth with a magnetic field that does not align with the axis of rotation and to the earth with a stronger or weaker magnetic field intensity. All of those cases have been founded to have occurred.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4BNVXPR-2&_user=10&_coverDate=03%2F15%2F2004&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1216013719&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=84a97acac5c6865097ecca21e5d71fd3



Geomagnetic moment variation and paleomagnetic excursions since 400 kyr BP: a stacked record from sedimentary sequences of the Portuguese margin

A paleomagnetic study was performed in clayey-carbonate sedimentary sequences deposited during the last 400 kyr on the Portuguese margin (Northeast Atlantic Ocean). Declination and inclination of the stable remanent magnetization present recurrent deviations from the mean geomagnetic field direction. The normalized intensity documents a series of relative paleointensity (RPI) lows recognized in other reference records. Three directional anomalies occurring during RPI lows chronologically correspond to the Laschamp excursion (42 kyr BP),the Blake event (115 to 122 kyr BP) and the Icelandic basin excursion (190 kyr BP). A fourth directional anomaly recorded at 290 kyr BP during another RPI low defines the ‘Portuguese margin excursion’. Four non-excursional RPI lows are recorded at the ages of the Jamaica/Pringle Falls,Mamaku,Calabrian Ridge 1,and Levantine excursions. The RPI record is characterized by a periodicity of approx. 100 kyr,paleointensity lows often coinciding with the end of interglacial stages. This record sets the basis of the construction of an authigenic 10Be/9Be record from the same sedimentary sequences [Carcaillet et al.,this issue].

sarongsong
2010-Feb-22, 05:16 AM
What definition of secular fits the thread title :confused:

G O R T
2010-Feb-22, 06:39 AM
William, It is exceedingly difficult to duscuss a broad subject when you are being so vague.

You refer to "burn marks" which seem to be refering to the Carolina bays and similar structures. What is your specific reason to bring them into this?

You mention 10 geomagnetic jerk events that have occurred in the last 5000 years and say that the geomagnetic jerks are abrupt changes in the geomagnetic field inclination. This is not specifically true. The 10 geomagnetic jerk events you refer to were locally recorded on the Portuguese margin. This is typical of geomagnetic anomalies and in accordance with the (geo)dynamo theory. Geomagnetic jerks occur frequently across the planet. Since the Earth's average dipole moment is a sumation of myriad local poles (anomalies) and permanently magnetized strata, the change in inclination of the dipole is usually quite small (the exception being during a reversal). Local inclination changes are merely artifacts of local anomalies unless broadly correlated.


My point here is that none of these "evidences" are well accepted (read this) (http://geology.geoscienceworld.org/cgi/content/abstract/20/5/399), nor are they directly relevant to whether the Earth's magnetic field influences global climate (Correlation does not imply causation).

I am not, by the way, saying the theory is wrong. I just see no actual evidence for it.

G O R T
2010-Feb-22, 06:48 AM
What definition of secular fits the thread title :confused:


http://dictionary.reference.com/browse/secular
sec·u·lar   /ˈsɛkyələr/ Show Spelled[sek-yuh-ler] Show IPA
–adjective
1.of or pertaining to worldly things or to things that are not regarded as religious, spiritual, or sacred; temporal: secular interests.
2.not pertaining to or connected with religion (opposed to sacred): secular music.
3.(of education, a school, etc.) concerned with nonreligious subjects.
4.(of members of the clergy) not belonging to a religious order; not bound by monastic vows (opposed to regular).
5.occurring or celebrated once in an age or century: the secular games of Rome.
6.going on from age to age; continuing through long ages.

hhEb09'1
2010-Feb-22, 01:34 PM
[URL="http://dictionary.reference.com/browse/secular"]sarongsong may be asking about William's emphasis on it being a periodic variation rather than a secular variation. Of course, long term secular change could be found to be found to be a component of very long term periodic change.

sarongsong
2010-Feb-22, 05:34 PM
Actually, I'd never encountered definitions 5 and 6 before and am surprised to encounter them in a science setting. Are they common definitions here?

hhEb09'1
2010-Feb-22, 06:26 PM
Yes, sorta. For instance, the earth's axis moves in various fashions--the Chandler wobble about every 14 months, or the seasonal wobble every 12 months, but there is a so-called secular drift that causes the pole to move that doesn't seem to be associated with anything periodic. Here's an example website:

http://en.wikipedia.org/wiki/Secular_variation

tusenfem
2010-Feb-22, 06:49 PM
GORT,

Ryskin's ocean current modulation of the geomagnetic field hyothesis is not correct. The geomagnetic field abruptly changed inclination 10 times in the last 5000 years. There is no mechanism that can abruptly change the ocean current 10 times in the last 5000 years.


Then why bring up that ridiculous in the first place? That is no way to start a discussion.



Now as to the affect of a geomagnetic field excursion on the planet's climate. The planet is very cold when the geomagnetic field excursion occurs. The GCR affect saturates. Additional GCR has less and less effect. More GCR does not create additional clouds. The change in the geomagnetic field inclination changes where the clouds are formed. That explains why there is unexplained warming and cooling when the inclination occurs. Further complicating the paleo analysis is the geomagnetic intensity can when it equalizes increase or decrease intensity depending on the hemisphere where the strike occurred.

What has sufficient power to abruptly change the inclination of the geomagnetic field 10 times in the last 5000 years?


How about the Earth's dynamo, which is a chaotic system?
The GCR is NOT as universally accepted as you claim it to be (though you prefer to make quick claims that it must have been "mis measurements" or "problems with the measurements" or such, in the AGW thread).



This is not a theoretical thread. There is a massive cycle event that is occurring that will have a significant affect on the biosphere. There is observational evidence of burn marks at multiple locations in the Northern Hemisphere that all coincide in time with the Younger Dryas abrupt cooling event. There is observational evidence of a massive ribbon of gas at the far edge of the solar system that is aligned at 90 degrees to the planet's orbits. There is the curious offset Uranus and Neptune planetary magnetic fields.


No, this will not be a "theoretical thread" this is just going to be another william thread, with lots and lots of out of context quotes, unfounded claims and leading interpretations which is not going to go anywhere, under the umbrella of the CSI method.



It seems logical that a cyclic abrupt change to the geomagnetic field would have a cyclic forcing function. As we have never seen an event that leaves massive burn marks on the surface of the planet, it likely seems unimaginable. The basic implication is that the sun from time to time becomes unstable. The solar instability it appears comes in a small, medium, large, and super large.


It may seem logical to you. And whoppa, there you come with the "massive burn marks" WHY? Because it is unimaginable for YOU. And then some sillyness about the sun.



Read through this paper which is the author's response to comments.

I think one would also need the commenting paper to understand the reply.

There are so many claims posited here as fact that it would almost shift this topic into ATM.

captain swoop
2010-Feb-22, 07:38 PM
What's doing the 'burning'? or have I mised something?

Ara Pacis
2010-Feb-22, 09:37 PM
What's doing the 'burning'? or have I mised something?

I think it's related to a hypothesis that suggested a large impact or airburst occured in North America at the end of the last glaciation that caused wildfires and contributed to the extinction of North American megafauna.

This article in ScienceDaily claims it's been disproven.
http://www.sciencedaily.com/releases/2009/01/090126173729.htm

ScienceDaily (Jan. 27, 2009) — New data disproves the recent theory that a large comet exploded over North America 12,900 years ago, causing a shock wave that travelled across North America at hundreds of kilometres per hour and triggering continent-wide wildfires.

Dr Sandy Harrison from the University of Bristol and colleagues tested the theory by examining charcoal and pollen records to assess how fire regimes in North America changed between 15 and 10,000 years ago, a time of large and rapid climate changes.

William
2010-Feb-23, 02:52 AM
How about the Earth's dynamo, which is a chaotic system?


Maybe we should defer starting a discussion until you understand the observations (paleoclimatic and geomagnetic). What has happened in the past? It is difficult to explain, as there are no modern analogies to compare with.

The past interglacial periods ended very, very, abruptly. Not gradually. We cannot imagine the severity or the rapidity of the change. The planet abruptly cools which cause deserts to increase. There is 20 to 30 times increase in the amount of dust that is deposited on the Greenland ice sheet when the event occurs.

During an event 70 kyrs ago the human population was reduced to around 2000 individuals (it is hypothesized due to a drought that lasted a couple of thousand years) which is believed to be the limit for a species to survive.

Attached below is a copy of the paper looks at the connection of the geomagnetic field changes in planetary climate.

Right it seems logical that the movement of the conductive core liquid would be chaotic. (There are no actual measurements of core movement so theories are basically unproven.) It seem difficult for a chaotic liquid core to create the rapid and cyclic geomagnetic field changes that are observed. I believe the liquid core time constant is around 3000 to 5000 years.


20 years ago what was been founded (rapid changes to the geomagnetic field and rapid climate changes) were believed to not be theoretically possible. i.e. Magnetic field changes and planetary climate changes occurred gradually over 1000s years.


http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf

korjik
2010-Feb-23, 06:55 AM
I believe the liquid core time constant is around 3000 to 5000 years.




Snipped by me

Your belief is irrelevant. Show that the time constant is in the low kyears or you have nothing.

tusenfem
2010-Feb-23, 12:57 PM
Read through this paper which is the author's response to comments.

For those who do not like to read responses to questions/comments they don't know, here is the paper commenting (http://esoads.eso.org/abs/2008E%26PSL.265..302B) (pdf available on request)

I will try to read it all today.

G O R T
2010-Feb-23, 01:42 PM
The planet abruptly cools which cause deserts to increase. As a general rule? Proof please. A number of present deserts were absent during glaciation.




It seem difficult for a chaotic liquid core to create the rapid and cyclic geomagnetic field changes that are observed. The core has been shown to be solid, not liquid. Geomagnetism would be from myriad rising currents in the mantle, each interacting with neighbors and contributing to the whole of the average field. Anomaly mapping started in 1944 due to the poor accuracy of inflight compass headings. Anomalies can affect compass headings by several points in both small and large areas. Furthermore they were quickly recognized as being dynamic, requiring updates.



20 years ago what was been founded (rapid changes to the geomagnetic field and rapid climate changes) were believed to not be theoretically possible. i.e. Magnetic field changes and planetary climate changes occurred gradually over 1000s years. I'll give you that this may have been the generally publicized view for major change since it probably does take a thousand years to create a major ice sheet or to reverse magnetic polarity (completely).


http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf


The global extent and time coincidence of some of these
features is a matter of debate and ongoing research
(begging for a much larger database).

jlhredshift
2010-Feb-23, 02:01 PM
If someone has already posted this link, please forgive me, but this is a presentation session at the fall 2009 AGU meeting dealing with secular solar variation. It is a long session and covers where the science is at this time.

http://www.agu.org/meetings/fm09/lectures/lecture_videos/U34A.shtml

hhEb09'1
2010-Feb-23, 02:03 PM
The core has been shown to be solid, not liquid. Geomagnetism would be from myriad rising currents in the mantle, each interacting with neighbors and contributing to the whole of the average field. The earth's inner core is solid, but its outer core is liquid. Gauss showed almost 200 years ago that the earth's magnetic field mainly originates in the core.

William
2010-Feb-24, 03:20 AM
As a general rule? Proof please. A number of present deserts were absent during glaciation.





http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf


Hi GORT,

The increase in desertification is occurs when the planet cools. There is increased precipitation when the planet is warmer. That is also try today. The IPCC predicts a net increase in precipitation if the planet warms.

http://www.jstor.org/pss/1558157


Dust: Climate’s Rosetta Stone by Wally Broecker


During the last glacial period, temperatures on Greenland’s high plateau were six to ten degrees Celsius lower during millennial duration episodes of intense cold than during the alternating intervals to moderate cold. The dust and sea salt contents of the ice underwent abrupt threefold shifts. Spurred by this discovery, geologists began a search to see whether these changes are recorded elsewhere on the planet. Columbia’s Gerard Bond showed that each of Greenland’s intervals of intense cold was matched by a pulse of debris carried to the northern Atlantic by icebergs. Colorado’s Julian Sachs and Scott Lehman, using alkenone paleothermometry, showed that surface ocean temperatures in the region around Bermuda underwent four-to-five-degree Celsius jumps matching those for Greenland. Rich Behl and Jim Kennett of the University of California astounded the paleoclimate world by demonstrating that these events had profound impacts on surface water temperature and deep water dissolved oxygen gas (O 2) content in the Santa Barbara basin. German scientists extended the geographic range of the impacts by showing that, just as off California, these jumps raised and lowered the O2 content of thermocline waters in the Arabian Sea.

Columbia’s Pierre Biscaye, using isotopic tracers, pinned down the source of the dust contained in Greenland ice. It came all the way from Asia’s Gobi Desert. Ed Brook and Jeff Severinghaus, while postdoctoral fellows in Mike Bender’s Rhode Island laboratory, showed that sympathetic changes in the atmosphere’s methane content likely reflected changes in the warmness and wetness of tropical soils and swamps. The conclusion drawn from these studies is that the impact of these abrupt climate jumps was surely felt throughout the north temperate zone and perhaps in the tropics as well.

jlhredshift
2010-Feb-24, 04:43 AM
Hi GORT,

The increase in desertification is occurs when the planet cools. There is increased precipitation when the planet is warmer. That is also try today. The IPCC predicts a net increase in precipitation if the planet warms.

http://www.jstor.org/pss/1558157

I agree that Dr. Broecker is a wonderful source, and great reading, for this information. I would encourage reading all of his papers and a vast majority are available on the web; I use GOOGLE Scholar.

Particularly in North America, the intense cold periods caused a shift in weather patterns to the south. Most likely a high pressure center set up over Canada and caused the jet stream to move south. The American Southwest experienced a wetter period during the Younger Dryas, for instance, and the increased precipitation contributed to the expansion and maintenance of Lake Bonneville and Lake Lahontan. The recently deglaciated upper Midwest and plains of Canada experienced dessication and loss of ground cover that led to the winds from the northwest distributing the Peoria Loess. In other words, the temperate zone shifted south and what was temperate dried out and what was desert became temperate. Rains fell, just not in the same place. There was not a large increase in the amount of true desert. As the Holocene warming began and continued the weather patterns shifted back north and restored the temperate climate that had existed before.

mugaliens
2010-Feb-24, 06:20 AM
One problem with Ryskin's hypothesize is there is no mechanism to cyclically abruptly change ocean currents.

We already know ocean currents change abruptly. It's chaos theory 101. They tend to be where the are while the forces which shift them slowly build. When they reach a certain threshold, they abruptly shift, just as rolling a marble slowly out of one vally reaches a point at the crest of the ravine where it plunges into another valley.

G O R T
2010-Feb-24, 11:35 AM
The earth's inner core is solid, but its outer core is liquid. Gauss showed almost 200 years ago that the earth's magnetic field mainly originates in the core.

Point taken. the convecting currents are in the outer core.

Source for Geodynamo: http://www.es.ucsc.edu/~glatz/geodynamo.html

G O R T
2010-Feb-24, 12:43 PM
William:


As a general rule? Proof please. A number of present deserts were absent during glaciation.

Again, as a general rule? This questions the exact meaning of the statement.
The planet abruptly cools which cause deserts to increase. There is 20 to 30 times increase in the amount of dust that is deposited on the Greenland ice sheet when the event occurs.



We know that the polar cell was extended during glaciation and the polar regions are mostly desert, but this does not seem to be the meaning of the statement about Gobi dust in Greenland. The Gobi, being landlocked far inland by mountains that block the Westerlies, would be desert under almost any climatic conditions. The Hadley cell contraction of the same period left huge and long lived lakes in the Sahara and American Southwest. You go on by mentioning that the Human bottleneck may have been caused by a lengthy drought. Drought where? Where is information on this?

I question the inclusion of many of your statements. They can be questionable in themselves, and are questionable as to how they relate to the subject. If you think these statements are important then they need to be specific in nature and relationship.

JohnD
2010-Feb-24, 07:28 PM
sarongsong,
Thank you for asking the question.
I have always taken "secular" as meaning worldly as an opposite to "religious".
My Concise OED says that it is derived from 'seaculum', a Latin word meaning an age or a generation, which explains its use in this application. Difficult to see how it came have the irreligious meaning.

John

Baud
2010-Feb-25, 01:05 AM
...'seaculum', a Latin word meaning an age or a generation

saecularis>saeculum : It means more exactly "century"


Difficult to see how it came have the irreligious meaning.

Secular: Living in the century (Designates the temporal power, justice of the state, as opposed to spiritual.)

is opposed to

Regular: subject to a rule of life, such as monks.

JohnD
2010-Feb-25, 09:32 PM
I would have thought that living day to day was what most people did in the Dark Ages. While the monks had a much longer term attitude, less anxiety about enough to eat, same routine every day, no children to feed, partner(life) to live with, partner(work) to live with. Much more century centred - more 'secular'?

And almost no one lives for a century. If they live about seventy years (and it was more like fifty) then about two thirds would see a century change, an 00 date. So most people live and lived in two centuries!

John

Baud
2010-Feb-26, 12:00 AM
I would have thought that living day to day was what most people did in the Dark Ages. While the monks had a much longer term attitude, less anxiety about enough to eat, same routine every day, no children to feed, partner(life) to live with, partner(work) to live with. Much more century centred - more 'secular'?
This is partialy true as there is also a distinction between:
Secular Clergy: made to parish priests, deacons, bishops, cardinals, etc.
Regular clergy: following the rule of a monastic order.

Clerics Regular live by a rule, outside the world, in monasteries or abbeys.
The secular clergy living "in the century", among the laity.

I would say that "in the century" means (was meaning) "in the world"

(I hope my poor English is understandable)

tusenfem
2010-Feb-26, 08:08 AM
Okay, let's stop the secular discussion here, and move back to the OP.

JohnD
2010-Feb-26, 08:31 PM
OK, all those who want to discuss 'secular', over this end of the bar!

http://www.bautforum.com/science-technology/101314-origin-secular.html#post1689521

John

William
2010-Feb-27, 04:16 AM
sarongsong may be asking about William's emphasis on it being a periodic variation rather than a secular variation. Of course, long term secular change could be found to be found to be a component of very long term periodic change.


Ryskin used the word secular to describe how the geomagnetic field changes in specific regions (i.e. The polarity of the field is changed in specific regions (similar to the current South Atlantic magnetic anomaly only stronger), the tilt of the field changes, and over time as the change is integrated by the liquid core and converted to a dipole field, the total intensity of the geomagnetic field changes (as opposed to regional changes in the field)) of the planet due to some cyclic forcing event.

A specific periodic forcing appears to change the geomagnetic field.

Look at the periodicity of the very strong abrupt climate change events. (There are also smaller cyclic changes such at the Little Ice Age and the Medieval warm period) Abrupt climate change requires an abrupt significant change to the planetary system to cause what is observed.

There is no explanation for what is forcing the planet's climate. One of the original hypotheses was that ocean currents were the forcing event. That hypothesis has been shown to be in correct. Ocean currents transport heat from the tropics to higher latitudes. It is not possible to have simultaneous cooling at the tropics and at higher latitudes if ocean currents were the cause.

Another problem with ocean currents is the change in planetary temperature is 3 to 5 times the greater than the energy transported by ocean currents. (The ocean current hypothesis was based on evidence that ocean currents do change when this event occurs.) It appears, however, that ocean currents are the tail and whatever is forcing the planet's climate is the dog.

The discovery of periodic abrupt climate change is relatively recent. (Say since 1990.)

The discovery of cycle abrupt geomagnetic field changes is in the last 10 years.


"The earliest Holocene abrupt climate changes occurred at 12,800, 8200, 5200, and 4200 B.P. . . ."
The 8200 B.P. event, "lasted four hundred years (6400-6000 B.C.) and, like the Younger Dryas, generated abrupt aridification and cooling in the North Atlantic and North America, Africa, and Asia (Alley et al. 1997; Barber et al. 1999; Hu et al. 1999; Street-Perrot and Perrot 1990).



http://esciencenews.com/articles/2009/06/18/ancient.drought.and.rapid.cooling.drastically.alte red.climate

http://www.pnas.org/content/103/28/10536.abstract


Two abrupt and drastic climate events, 700 years apart and more than 45 centuries ago, are teasing scientists who are now trying to use ancient records to predict future world climate. The events – one, a massive, long-lived drought believed to have dried large portions of Africa and Asia, and the other, a rapid cooling that accelerated the growth of tropical glaciers – left signals in ice cores and other geologic records from around the world.



A professor of geological sciences at Ohio State and a researcher with the Byrd Polar Research Center, Thompson (my comment a link to Lonnie Thompson's paper is attached below) points to markers in numerous records suggesting that the climate was altered suddenly some 5,200 years ago with severe impacts. Thompson points to a study of tree rings from Ireland and England that span a period of 7,000 years. The point in that record when the tree rings were narrowest – suggesting the driest period experienced by the trees – was approximately 5,200 years ago.


He points to ice core records showing the ratio of two oxygen isotopes retrieved from the ice fields atop Africa’s Mount Kilimanjaro. A proxy for atmospheric temperature at the time snow fell, the records are at their lowest 5,200 years before now. The first of the two tantalizing events is apparent in an ice core drilled in 1993 from an ice field in the Peruvian Andes called Huascaran. Within that core, they found a thick band of dust particles, most smaller than a micron in diameter, the concentration of which was perhaps 150 times greater than anywhere else in the core. That band dated back to 4,500 years ago.


http://sheridan.geog.kent.edu/geog41066/7-Overpeck.pdf


ABRUPT CHANGE IN EARTH’S CLIMATE SYSTEM
Abrupt shifts between warm and cold states punctuate the interval between 20 to 75 ka) in the Greenland isotope record, with shifts of 5◦–15◦C occurring in decades or less (Figure 1). These alternations were identified in some of the earliest ice core isotopic studies [e.g., (22)] and were replicated and more precisely dated by subsequent work (23). Further analysis of diverse records has distinguished two types of millennial events (13). Dansgaard/Oeschger (D/O) events are alternations between warm (interstadial) and cold (stadial) states that recur approximately every 1500 years, although this rhythm is variable. Heinrich events are intervals of extreme cold contemporaneous with intervals of ice-rafted detritus in the northern North Atlantic (24–26); these recur irregularly on the order of ca. 10,000 years apart and are typically followed by the warmest D/O interstadials.



Both Heinrich and D/O events exhibit clear global impacts. These patterns have been summarized in several studies [e.g., (26, 34)]. Although the pattern of influence appears to differ between these types of anomaly, a clear interpretation of these differences, particularly in terms of distinguishing physical mechanisms, has not been developed. As Hemming (26) notes, different global patterns of impact may simply reflect proxy-specific or site-specific limitations such as sensitivity and response time. In general, however, a cold North Atlantic corresponds with a colder, drier Europe, weaker Asian summer monsoon, saltier northwestern tropical Pacific, drier northern South America, colder/wetter western North America, cooler eastern subtropical Pacific, and warmer South Atlantic and Antarctic. Table 1 summarizes the main impacts of a cold North Atlantic (stadial) on key regions and systems.

http://www.geo.arizona.edu/palynology/geos462/8200yrevent.html


The 8200-year Climate Event
This figure shows snow accumulation and isotopically inferred temperature records in the Greenland GISP2 ice core and a temperature record derived from oxygen isotope measurements of fossil shells in the sediments of Lake Ammersee, southern Germany. These records all show a major climatic instability event which occurred around 8200 years ago, during the Holocene. The event was large both in magnitude, as reflected by a temperature signal in Greenland of order 5 C, and in its geographical extent, as indicated by the close correlation of the signal in these two locations. The dramatic event is also seen in the methane record from Greenland (not shown here) indicating possible major shifts in hydrology and land cover in lower latitudes. source: Von Grafenstein et al (1998) Climate Dynamics, 14, 73-81.




Abrupt tropical cooling ~8,000 years ago
"We drilled a sequence of exceptionally large, well-preserved Porites corals within an uplifted palaeo-reef in Alor, Indonesia, with Th-230 ages spanning the period 8400 to 7600 calendar years before present (Figure 2). The corals lie within the Western Pacific Warm Pool, which at present has the highest mean annual temperature in the world's ocean. Measurements of coral Sr/Ca and oxygen 18 isotopes at 5-year sampling increments for five of the fossil corals (310 annual growth increments) have yielded a semi-continuous record spanning the 8.2 ka event. The measurements (Figure 2) show that sea-surface temperatures were essentially the same as today from 8400 to 8100 years ago, followed by an abrupt ~3C cooling over a period of ~100 years, reaching a minimum ~8000 years ago. The cooling calculated from coral oxygen 18 isotopes is similar to that derived from Sr/Ca. The exact timing of the termination of the cooling event is not yet known, but a coral dated as 7600 years shows sea-surface temperatures similar to those of today."

G O R T
2010-Mar-01, 09:22 AM
Ryskin used the word secular to describe how the geomagnetic field changes in specific regions (i.e. The polarity of the field is changed in specific regions (similar to the current South Atlantic magnetic anomaly only stronger), the tilt of the field changes, and over time as the change is integrated by the liquid core and converted to a dipole field, the total intensity of the geomagnetic field changes (as opposed to regional changes in the field)) of the planet due to some cyclic forcing event.

A specific periodic forcing appears to change the geomagnetic field.

I have no access to the data concerning proposed recent periodic magnetic changes in the mentioned (or any) specific location. The big picture of the Earth's magnetic reversals show no periodicity (USGS and others). Are you saying that minor field changes have greater effect than the reversals?



Look at the periodicity of the very strong abrupt climate change events. (There are also smaller cyclic changes such at the Little Ice Age and the Medieval warm period) Abrupt climate change requires an abrupt significant change to the planetary system to cause what is observed.

There is no explanation for what is forcing the planet's climate. One of the original hypotheses was that ocean currents were the forcing event. That hypothesis has been shown to be in correct. Ocean currents transport heat from the tropics to higher latitudes. It is not possible to have simultaneous cooling at the tropics and at higher latitudes if ocean currents were the cause.

There are any number of explanations for what is forcing the planet's climate. Simultaneous cooling is the obvious outcome of cooling in the tropics, a simple reduction in present patterns of surface heat transport is the main theory in which this is an issue.



Another problem with ocean currents is the change in planetary temperature is 3 to 5 times the greater than the energy transported by ocean currents. (The ocean current hypothesis was based on evidence that ocean currents do change when this event occurs.) It appears, however, that ocean currents are the tail and whatever is forcing the planet's climate is the dog.

Since the deep oceans contain some 800+ times the thermal capacity of the atmosphere and surface waters, there is no reason to discount them by simply looking at surface heat transport effects.

William
2010-Mar-02, 02:50 AM
I have no access to the data concerning proposed recent periodic magnetic changes in the mentioned (or any) specific location. The big picture of the Earth's magnetic reversals show no periodicity (USGS and others). Are you saying that minor field changes have greater effect than the reversals?


There appear to be three paradigm shifts.

The first was the discovery of cyclic abrupt climate change which occurred in the 1990s. There are no modern analogs explain what abrupt climate change is. During the Younger Dryas the temperature in North America dropped 18F. New England went from 2 to 3 months of winter to 11 months. The majority of this cooling occurred in three steps over 15 years. In 45 years the cooling reached equilibrium. The planet was cooled (changed from interglacial warm to glacial cold when insolation at the critical 65N was at its greatest in the summer) for over a 1000 years.

The climate paradigm shift is abrupt planetary cooling is cyclic and very fast. That makes sense as there needs to be a very strong change to change the climate. If you check the AWG thread ARI and I are having a discussion about planetary feedback. The data shows the planet's response to a forcing change is increase or decrease planetary clouds to regulate planetary data. If planetary feedback to change in forcing is negative then a very strong forcing change is required to cause what is observed.

The second paradigm shift involve the geomagnetic field. Based on the assumed mechanism geomagnetic field changes were expected to be gradual over 1000s of years. What was been found is the geomagnetic field changes very rapidly and cyclically.

Comment:
The geomagnetic field reversals do exhibit a pattern. The current average time between reversals is 200 kyrs, yet there are periods when the planet went 40 million years without a reversal. Something is obviously effecting the reversal rate.

http://en.wikipedia.org/wiki/Geomagnetic_reversal#Changing_frequency_of_geomagn etic_reversals_over_time


Geomagnetic polarity time scale
Changing frequency of geomagnetic reversals over time

The rate of reversals in the Earth's magnetic field has varied widely over time. 72 million years ago (Ma), the field reversed 5 times in a million years. In a 4-million-year period centered on 54 Ma, there were 10 reversals; at around 42 Ma, 17 reversals took place in the span of 3 million years. In a period of 3 million years centering on 24 Ma, 13 reversals occurred. No fewer than 51 reversals occurred in a 12-million-year period, centering on 15 million years ago. These eras of frequent reversals have been counterbalanced by a few "superchrons" – long periods when no reversals took place.[4]

It had generally been assumed that the frequency of geomagnetic reversals is random; in 2006, a team of physicists at the University of Calabria found that the reversals conform to a Lévy distribution, which describes stochastic processes with long-ranging correlations between events in time.[5]
[edit] Cretaceous Long Normal Superchron

A long period of time during which there were no magnetic pole reversals, the Cretaceous Long Normal (also called the Cretaceous Superchron or C34) lasted for almost 40 million years, from about 120 to 83 million years ago. This time period included stages of the Cretaceous period from the Aptian through the Santonian.

An interesting trend can be seen when looking at the frequency of magnetic reversals approaching and following the Cretaceous Long Normal. The frequency steadily decreased prior to the period, reaching its low point (no reversals) during the period. Following the Cretaceous Superchron the frequency of reversals slowly increased over the next 80 million years, to the present.

The third paradigm shift is related to the sun and to stars in general. Something must force the geomagnetic field which in turn forces the planet climate. The changes in geomagnetic field are too fast and too localized to be due to internal forces. (There is no mechanism to cyclically change core motion to match the observations.)


http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf

Are there connections between the Earth's magnetic field and climate?



Archeomagnetic jerks are found around 1400, 800, 200AD and 800 BC. Subsequent work [61] has added an event around 1600, with other less robust possibilities at 1800, 600 AD and 350 BC. This implies 4 rather clear events in the past two millennia (i.e. a “repeat time” on the order of 500 yr, a time-constant characteristic of secular variation of the equatorial dipole field — e.g. [57]) if only the more robust events are included. The number goes to 7 if all suggested events are included, implying a time constant of 200–300 yr, not very different from the duration of the events themselves and more characteristic of non-dipole secular variation (though see [53]). In this paper, we restrict ourselves to the better-identified events, which remain short and rather rare on the time scales considered.

There is a good correspondence between jerk times (particularly their rising period) and advances in glaciers. The correlation between cold events and archeomagnetic jerks is significant at 1600, ~1350, ~800 AD and ~800 BC. Very recently, Gallet et al. [64] have extended the database to 3000 BC in the Middle East, and found older jerk events at ~1600, ~2100 and ~2700 BC (Fig. 5; see also [59]). They found that these geomagnetic variations coincide in time with cooling periods detected in the North Atlantic from ice-rafted debris [65].



Also, we wish to recall that evidence of a correlation between archeomagnetic jerks and cooling events (in a region extending from the eastern North Atlantic to the Middle East) now covers a period of 5 millenia and involves 10 events (see f.i. Figure 1 of Gallet and Genevey, 2007). The climatic record uses a combination of results from Bond et al (2001), history of Swiss glaciers (Holzhauser et al, 2005) and historical accounts reviewed by Le Roy Ladurie (2004). Recent high-resolution paleomagnetic records (e.g. Snowball and Sandgren, 2004; St-Onge et al., 2003) and global geomagnetic field modeling (Korte and Constable, 2006) support the idea that part of the centennial-scale fluctuations in 14C production may have been influenced by previously unmodeled rapid dipole field variations. In any case, the relationship between climate, the Sun and the geomagnetic field could be more complex than previously imagined. And the previous points allow the possibility for some connection between the geomagnetic field and climate over these time scales.



Point 4: We first reiterate the fact that the “claims” made in our paper regarding correlations between cooling periods and archeomagnetic jerks were actually put forward by Gallet et al (2005, 2006). We do note that the causal relationship between cosmic ray flux and cloud cover suggested by Marsh and Svensmark (2000) would result in a correlation opposite to the one we find if the field geometry were axial and dipolar and this is precisely why we propose a mechanism of dipole tilt or non dipole geometry to interpret our observations. Gallet et al (2005) write: “ Another hypothesis is to assume that the incoming charged particles are deflected towards the poles, where the overall low humidity level due to cold temperatures limits cloud formation. If archeomagnetic jerks indeed correspond to periods of strongly inclined dipole, then the charged particles would interact with more humid air from lower latitude environments, leading to significantly larger cloud production and cooling.” And if this happens, there is no need to “overcome the more direct effect", as (mis)understood by BD07 (who seem to understand that a growing axial dipole is superimposed on a tilted dipole, which is not the case).


It is therefore not surprising that the tuned curve should reveal the link between solaractivity and 18O. It is moreover interesting to note that this correlation, obtained on an Alpine stalagmite, and therefore evidence of the influence of solar variability on climate, is also found in proxies from other regions around the globe: correlation between times of solar minima and cold episodes in western Europe (Magny, 1993; Holzhauser et al, 2005), modulation of precipitation in the tropics in Northern South America and Yucatan (Haug et al, 2001), in Eastern Africa (Verschuren et al, 2000), and Arabia (Neff et al, 2001); influence on droughts in North America (Yu and Ito, 1999).